Classical Genetics

Early Theories

Pangenesis – egg and sperm consist of particles, which develop into parts of the body where they were derived – Aristole

Homunculus – miniature person in sperm - Leeuwenhoek - Egg contains the entire persons – de Graaf

Blending of parental traits – lead to our current view of inheritance.

Mendel – The Father of Genetics

•Was a monk – only way he could further his education

•He bred, tended, and analyzed over 28000 pea plants.

•Started with true breeding plants.

Mendel’s LawsLaw of Segregation – all individuals have two copies of each factor (gene). These copies separate randomly during gamete formation and each gamete only gets one copy.

Law of Independent Assortment – two alleles for one genes segregate independently of the alleles for other genes during gamete formation.

Key TermsMonohybrid cross – looking at only SINGLE characteristic

Dihybrid cross – looking at TWO characteristics

Alleles –same gene but different instruction

More Terms - YIPEEDominant – genes which determine the expression of the trait

Recessive – genes which are overruled by dominant genes

Complete Dominance – one gene shows over the other

More Terms – Having fun yet?!

Genotype – combination of alleles of any given trait

Phenotype – physical form you can observe.

Guess What? – MORE TERMS!!!

Homozygous – two identical alleles.

Heterozygous – two different alleles for each trait

Almost Done with Terms - Punnett Square

Test Cross – a cross between an organism of unknown genotype and a homozygous recessive

Generations - LabellingParental – P generation First filial – F1 – the offspring from parental generationSecond filial – F2 – the offspring from the F1

In cats, long hair is recessive to short hair. A true-breeding (homozygous) short-haired male is mated to a long-haired female. What will their kittens look like?

Two cats are mated. One of the parent cats is long-haired (recessive allele). The litter which results contains two short-haired and three long-haired kittens. What does the second parent look like, and what is its genotype?

Mrs. And Mr. Smith both have widow’s peaks (dominant). Their first child also has a widow’s peak, but their second child doesn’t. Mr. Smith accuses Mrs. Smith of being unfaithful to him. Is he necessarily justified? Why or why not? Work the genetics problem predicting the frequencies of the versions of this trait among their prospective children.